Hair growing on rear diff. in 94 325

[Vic Mayer]

I don't know what is going on with the rear end in my 94 325Is.
I park the car for the winter months. My garage is not heated but
it is dry. I was looking under the car at something when I noticed that long hairs growing off the rear end to the floor, At first I thought that it was spider webs,I cleaned them off and a few weeks later they were back. The rear end is getting all white & fuzzy. Is there any thing I can do to stop this from happening.The car has a lot of miles on it ,but is in good shape. I have had many BMW's that I parked for the winter and never had this type of thing happen. Thanks for the help.

[LiquidBMW76]

sounds almost like mold